The present application is directed to window panes and more particularly to high-performance window panes and methods for forming high-performance window panes.
An approach to improving an existing single pane window's performance is to replace the entire window (frame, sash, and glazing) with a more modern window incorporating an advanced insulated glass unit (IGU). In addition to being double pane windows, IGUs also incorporate a low emissivity (“low-e”) coating on at least one of the panes.
Emission of thermal radiation by an unimproved glass pane is a major source of heat loss. The low-e coating can reduce this loss. Additionally, filling the space between the panes with inert gases such as argon is intended to further improve IGU insulation by decreasing thermal conductance.
Despite these designs, single pane windows are being replaced by more advanced multi-pane windows fairly slowly in the United States and elsewhere. The cost of window replacement is one issue slowing down replacement; another is that the change in a building's appearance may preclude replacement of single pane windows by IGUs for esthetic and historical reasons (including location in an historical district), or due to homeowner association covenants. Still further, non-structural curtain walls of buildings are not constructed to support the additional weight of IGUs, which is typically more than double that of the single pane window which it would replace.
With regard to single pane window retrofits, these can be made with adhesive window films that modify the optical properties of existing single pane windows both in buildings and vehicles. These adhesives typically include a low-e coating. However interior condensation resistance is diminished by the low-e layer. What is meant by interior condensation resistance is that, everything else being equal, the low-e layer effectively decreases the temperature of the pane, resulting in condensation on the pane at higher outdoor temperatures than without low-e layer. Condensation also affects emissivity, and interior surface low-e layers are most effective on windows without condensation.
Exterior storm windows can improve the efficiency of a single pane window. With the addition of a low-e coating they can be nearly as efficient as an IGU. Disadvantages of the exterior storm windows are their change to the exterior appearance of a building, and interference with opening and closing of existing windows, as well as cost.
Interior panels that are sealed against the existing window frame are also believed to be less expensive than full replacement, and attempt to duplicate qualities of IGUs for soundproofing, comfort, and efficiency. They may however interfere with the operation of the original window and with existing shades, have issues with cold-weather condensation of water, and also have appearance and cost issues.
Certain alternative window panes employ silica aerogels in sealed pane assemblies (i.e., where aerogels are synthetic porous ultralight materials derived from a gel, where the liquid component of the gel has been replaced with a gas). However, these are expected to share similar drawbacks with IGUs due to the need to use a seal for prevention of water adsorption and mechanical damage to the silica aerogel in consideration of its low tensile strength, among other drawbacks.
In view of the issues of existing and proposed window panes and installations, it is considered useful to develop and manufacture improved single pane windows.